Fast rate-distortion optimized quantization

ABSTRACT

A system and method for applying Rate Distortion Optimized Quantization (RDOQ) is disclosed. In one example, there is provided a method that includes determining at least one prediction type and at least one partition type for use in encoding at least one block of video data. The method further includes applying a non-RDOQ quantization scheme to the at least one block of the video data. The non-RDOQ quantization scheme may be applied during the determination of the at least one prediction type and the at least one partition type. The method further includes applying an RDOQ quantization scheme to the at least one block upon determining the at least one prediction type and the at least one partition type.

INCORPORATION BY REFERENCE TO PRIORITY APPLICATION(S)

This application claims the benefit of U.S. Provisional Application No.62/129,700, filed Mar. 6, 2015.

TECHNICAL FIELD

This disclosure relates to the field of video coding and compression,and particularly to reducing the complexity of rate-distortion optimizedquantization (RDOQ) technique applied in High-Efficiency Video Coding(HEVC).

BACKGROUND

Digital video capabilities can be incorporated into a wide range ofdevices, including digital televisions, digital direct broadcastsystems, wireless broadcast systems, personal digital assistants (PDAs),laptop or desktop computers, digital cameras, digital recording devices,digital media players, video gaming devices, video game consoles,cellular or satellite radio telephones, video teleconferencing devices,and the like. Digital video devices implement video compressiontechniques, such as those described in the standards defined by MPEG-2,MPEG-4, ITU-T H.263, ITU-T H.264/MPEG-4, Part 10, Advanced Video Coding(AVC), the High Efficiency Video Coding (HEVC) standard, and extensionsof such standards. The video devices may transmit, receive, encode,decode, and/or store digital video information more efficiently byimplementing such video coding techniques.

HEVC is the international standard for video coding developed by theJoint Collaborative Team on Video Coding (JCT-VC) of ITU-T WP3/16 andISO/IEC JTC 1/SC 29/WG 11. The latest reference software HEVC Test Model(HM) version 16.0 is available at:https://hevc.hhi.fraunhofer.de/svn/svn_HEVCSoftware/tags/HM-16.0/

SUMMARY

The systems, methods and devices of this disclosure each have severalinnovative aspects, no single one of which is solely responsible for thedesirable attributes disclosed herein.

In one aspect, an apparatus for applying Rate Distortion OptimizedQuantization (RDOQ) includes a memory and a processor in communicationwith the memory. The memory is configured to store a set of quantizationschemes for use in encoding at least one block of video data, the setincluding an RDOQ quantization scheme and a non-RDOQ quantizationscheme. The processor is configured to: determine at least oneprediction type and at least one partition type for use in encoding theat least one block of video data; apply the non-RDOQ quantization schemeto the at least one block of the video data during the determination ofthe at least one prediction type and the at least one partition type;and apply the RDOQ quantization scheme to the at least one block upondetermining the at least one prediction type and the at least onepartition type.

In another aspect, there is provided a method that includes: determiningat least one prediction type and at least one partition type for use inencoding at least one block of video data; applying a non-RDOQquantization scheme to the at least one block of the video data duringthe determination of the at least one prediction type and the at leastone partition type; and applying an RDOQ quantization scheme to the atleast one block upon determining the at least one prediction type andthe at least one partition type.

In another aspect, a non-transitory computer readable storage mediumcontains instructions that, when executed, cause a processor of a deviceto: determine at least one prediction type and at least one partitiontype for use in encoding at least one block of video data; apply anon-RDOQ quantization scheme to the at least one block of the video dataduring the determination of the at least one prediction type and the atleast one partition type; and apply an RDOQ quantization scheme to theat least one block upon determining the at least one prediction type andthe at least one partition type.

In another aspect, there is provided a video coding device thatincludes: means for determining at least one prediction type and atleast one partition type for use in encoding at least one block of videodata; means for applying a non-RDOQ quantization scheme to the at leastone block of the video data during the determination of the at least oneprediction type and the at least one partition type; and means forapplying an RDOQ quantization scheme to the at least one block upondetermining the at least one prediction type and the at least onepartition type.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a block diagram illustrating an example video encoding anddecoding system that may utilize techniques in accordance with aspectsdescribed in this disclosure.

FIG. 1B is a block diagram illustrating another example video encodingand decoding system that may perform techniques in accordance withaspects described in this disclosure.

FIG. 2A is a block diagram illustrating an example of a video encoderthat may implement techniques in accordance with aspects described inthis disclosure.

FIG. 2B is a block diagram illustrating an example of a video encoderthat may implement techniques in accordance with aspects described inthis disclosure.

FIG. 3A is a block diagram illustrating an example of a video decoderthat may implement techniques in accordance with aspects described inthis disclosure.

FIG. 3B is a block diagram illustrating an example of a video decoderthat may implement techniques in accordance with aspects described inthis disclosure.

FIG. 4 is an illustration of exemplary scan patterns in HEVC.

FIG. 5 is a flowchart of an exemplary embodiment of a process forperforming RDOQ in accordance with aspect(s) described in thisdisclosure.

DETAILED DESCRIPTION

In general, this disclosure relates to the selective utilization of therate-distortion optimized quantization (RDOQ) technique, which is anencoder-side optimization technique for achieving superior videocompression efficiency. However, compared to conventional quantizationschemes, the complexity of RDOQ is high because much more complexcomputations are involved, and such complex computations are performedmultiple times, such as, for example, for each coefficient group (CG) inthe context of High Efficiency Video Coding (HEVC).

With conventional RDOQ implementations in the HEVC Test Model (HM), RDOQmay be performed multiple times during a decision process. For example,RDOQ may be performed for every intra prediction mode of every blockduring an intra-prediction mode decision process. In another example,RDOQ may be performed for each partition type during a partition typedecision process. However, the best prediction type and/or partitiontype of each block is relatively stable whether RDOQ is performed ornot. As such, RDOQ may not need to be performed for every predictiontype and/or partition type of every block during the decision process.Therefore, a more efficient RDOQ technique is desired.

In the description below, H.264/AVC techniques related to certainembodiments are described; the HEVC standard and related techniques arealso discussed. While certain embodiments are described herein in thecontext of the HEVC and/or H.264 standards, one having ordinary skill inthe art may appreciate that systems and methods disclosed herein may beapplicable to any suitable video coding standard. For example,embodiments disclosed herein may be applicable to one or more of thefollowing standards (e.g., including standards developed byInternational Telecommunication Union Telecommunication StandardizationSector [ITU-T] Video Coding Experts Group [VCEG] or InternationalOrganization for Standardization/International ElectrotechnicalCommission [ISO/IEC] Moving Pictures Experts Group [MPEG]): ITU-T H.261,ISO/IEC MPEG-1 Visual, ITU-T H.262 or ISO/IEC MPEG-2 Visual, ITU-TH.263, ISO/IEC MPEG-4 Visual and ITU-T H.264 (also known as ISO/IECMPEG-4 AVC), including its Scalable Video Coding (SVC) and MultiviewVideo Coding (MVC) extensions.

HEVC generally follows the framework of previous video coding standardsin many respects. The unit of prediction in HEVC is different from theunits of prediction (e.g., macroblocks) in certain previous video codingstandards. In fact, the concept of macroblock does not exist in HEVC asunderstood in certain previous video coding standards. A macroblock isreplaced by a hierarchical structure based on a quadtree scheme, whichmay provide high flexibility, among other possible benefits. Forexample, within the HEVC scheme, three types of blocks, Coding Unit(CU), Prediction Unit (PU), and Transform Unit (TU), are defined. CU mayrefer to the basic unit of region splitting. CU may be consideredanalogous to the concept of macroblock, but HEVC does not restrict themaximum size of CUs and may allow recursive splitting into four equalsize CUs to improve the content adaptively. PU may be considered thebasic unit of inter/intra prediction, and a single PU may containmultiple arbitrary shape partitions to effectively code irregular imagepatterns. TU may be considered the basic unit of transform. TU can bedefined independently from the PU; however, the size of a TU may belimited to the size of the CU to which the TU belongs. This separationof the block structure into three different concepts may allow each unitto be optimized according to the respective role of the unit, which mayresult in improved coding efficiency.

For purposes of illustration only, certain embodiments disclosed hereinare described with examples including only two layers (e.g., a lowerlayer such as a BL, and a higher layer such as an EL) of video data. A“layer” of video data may generally refer to a sequence of pictureshaving at least one common characteristic, such as a view, a frame rate,a resolution, or the like. For example, a layer may include video dataassociated with a particular view (e.g., perspective) of multi-viewvideo data. As another example, a layer may include video dataassociated with a particular layer of scalable video data. Thus, thisdisclosure may interchangeably refer to a layer and a view of videodata. For example, a view of video data may be referred to as a layer ofvideo data, and a layer of video data may be referred to as a view ofvideo data. In addition, a multi-layer codec (also referred to as amulti-layer video coder or multi-layer encoder-decoder) may jointlyrefer to a multiview codec or a scalable codec (e.g., a codec configuredto encode and/or decode video data using MV-HEVC, 3D-HEVC, SHVC, oranother multi-layer coding technique). Video encoding and video decodingmay both generally be referred to as video coding. It should beunderstood that such examples may be applicable to configurationsincluding multiple BLs, RLs, and/or ELs. In addition, for ease ofexplanation, the following disclosure includes the terms “frames” or“blocks” with reference to certain embodiments. However, these terms arenot meant to be limiting. For example, the techniques described belowcan be used with any suitable video units, such as blocks (e.g., CU, PU,TU, macroblocks, etc.), slices, frames, etc.

Video Coding Standards

A digital image, such as a video image, a TV image, a still image or animage generated by a video recorder or a computer, may consist of pixelsor samples arranged in horizontal and vertical lines. The number ofpixels in a single image is typically in the tens of thousands. Eachpixel typically contains luminance and chrominance information. Withoutcompression, the sheer quantity of information to be conveyed from animage encoder to an image decoder would render real-time imagetransmission impossible. To reduce the amount of information to betransmitted, a number of different compression methods, such as JPEG,MPEG and H.263 standards, have been developed.

Video coding standards include ITU-T H.261, ISO/IEC MPEG-1 Visual, ITU-TH.262 or ISO/IEC MPEG-2 Visual, ITU-T H.263, ISO/IEC MPEG-4 Visual andITU-T H.264 (also known as ISO/IEC MPEG-4 AVC), including its SVC andMVC extensions.

In addition, a video coding standard, namely HEVC, is being developed bythe Joint Collaboration Team on Video Coding (JCT-VC) of ITU-T VCEG andISO/IEC MPEG. The full citation for the HEVC Draft 10 is documentJCTVC-L1003, Bross et al., “High Efficiency Video Coding (HEVC) TextSpecification Draft 10,” Joint Collaborative Team on Video Coding(JCT-VC) of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11, 12th Meeting:Geneva, Switzerland, Jan. 14, 2013 to Jan. 23, 2013. The multiviewextension to HEVC, namely MV-HEVC, and the scalable extension to HEVC,named SHVC, are also being developed by the JCT-3V (ITU-T/ISO/IEC JointCollaborative Team on 3D Video Coding Extension Development) and JCT-VC,respectively.

Video Coding System

Various aspects of the novel systems, apparatuses, and methods aredescribed more fully hereinafter with reference to the accompanyingdrawings. This disclosure may, however, be embodied in many differentforms and should not be construed as limited to any specific structureor function presented throughout this disclosure. Rather, these aspectsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the disclosure to those skilled in theart. Based on the teachings herein one skilled in the art shouldappreciate that the scope of the disclosure is intended to cover anyaspect of the novel systems, apparatuses, and methods disclosed herein,whether implemented independently of, or combined with, any other aspectof the present disclosure. For example, an apparatus may be implementedor a method may be practiced using any number of the aspects set forthherein. In addition, the scope of the present disclosure is intended tocover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition toor other than the various aspects of the present disclosure set forthherein. It should be understood that any aspect disclosed herein may beembodied by one or more elements of a claim.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Although some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description of the preferred aspects. Thedetailed description and drawings are merely illustrative of thedisclosure rather than limiting, the scope of the disclosure beingdefined by the appended claims and equivalents thereof.

The attached drawings illustrate examples. Elements indicated byreference numbers in the attached drawings correspond to elementsindicated by like reference numbers in the following description. Inthis disclosure, elements having names that start with ordinal words(e.g., “first,” “second,” “third,” and so on) do not necessarily implythat the elements have a particular order. Rather, such ordinal wordsare merely used to refer to different elements of a same or similartype.

FIG. 1A is a block diagram that illustrates an example video codingsystem 10 that may utilize techniques in accordance with aspectsdescribed in this disclosure. As used described herein, the term “videocoder” refers generically to both video encoders and video decoders. Inthis disclosure, the terms “video coding” or “coding” may refergenerically to video encoding and video decoding. In addition to videoencoders and video decoders, the aspects described in the presentapplication may be extended to other related devices such as transcoders(e.g., devices that can decode a bitstream and re-encode anotherbitstream) and middleboxes (e.g., devices that can modify, transform,and/or otherwise manipulate a bitstream).

As shown in FIG. 1A, video coding system 10 includes a source device 12that generates encoded video data to be decoded at a later time by adestination device 14. In the example of FIG. 1A, the source device 12and destination device 14 are on separate devices—specifically, thesource device 12 is part of a source device, and the destination device14 is part of a destination device. It is noted, however, that thesource and destination devices 12, 14 may be on or part of the samedevice, as shown in the example of FIG. 1B.

With reference once again, to FIG. 1A, the source device 12 and thedestination device 14 may respectively comprise any of a wide range ofdevices, including desktop computers, notebook (e.g., laptop) computers,tablet computers, set-top boxes, telephone handsets such as so-called“smart” phones, so-called “smart” pads, televisions, cameras, displaydevices, digital media players, video gaming consoles, video streamingdevice, or the like. In various embodiments, the source device 12 andthe destination device 14 may be equipped for wireless communication.

The destination device 14 may receive, via a link 16, the encoded videodata to be decoded. The link 16 may comprise any type of medium ordevice capable of moving the encoded video data from the source device12 to the destination device 14. In the example of FIG. 1A, the link 16may comprise a communication medium to enable the source device 12 totransmit encoded video data directly to the destination device 14 inreal-time. The encoded video data may be modulated according to acommunication standard, such as a wireless communication protocol, andtransmitted to the destination device 14. The communication medium maycomprise any wireless or wired communication medium, such as a radiofrequency (RF) spectrum or one or more physical transmission lines. Thecommunication medium may form part of a packet-based network, such as alocal area network, a wide-area network, or a global network such as theInternet. The communication medium may include routers, switches, basestations, or any other equipment that may be useful to facilitatecommunication from the source device 12 to the destination device 14.

Alternatively, encoded data may be output from an output interface 22 toan optional storage device 31. Similarly, encoded data may be accessedfrom the storage device 31 by an input interface 28, for example, of thedestination device 14. The storage device 31 may include any of avariety of distributed or locally accessed data storage media such as ahard drive, flash memory, volatile or non-volatile memory, or any othersuitable digital storage media for storing encoded video data. In afurther example, the storage device 31 may correspond to a file serveror another intermediate storage device that may hold the encoded videogenerated by the source device 12. The destination device 14 may accessstored video data from the storage device 31 via streaming or download.The file server may be any type of server capable of storing encodedvideo data and transmitting that encoded video data to the destinationdevice 14. Example file servers include a web server (e.g., for awebsite), a File Transfer Protocol (FTP) server, network attachedstorage (NAS) devices, or a local disk drive. The destination device 14may access the encoded video data through any standard data connection,including an Internet connection. This may include a wireless channel(e.g., a wireless local area network [WLAN] connection), a wiredconnection (e.g., a digital subscriber line (DSL), a cable modem, etc.),or a combination of both that is suitable for accessing encoded videodata stored on a file server. The transmission of encoded video datafrom the storage device 31 may be a streaming transmission, a downloadtransmission, or a combination of both.

The techniques of this disclosure are not limited to wirelessapplications or settings. The techniques may be applied to video codingin support of any of a variety of multimedia applications, such asover-the-air television broadcasts, cable television transmissions,satellite television transmissions, streaming video transmissions, e.g.,via the Internet (e.g., dynamic adaptive streaming over HypertextTransfer Protocol (HTTP), etc.), encoding of digital video for storageon a data storage medium, decoding of digital video stored on a datastorage medium, or other applications. In some examples, video codingsystem 10 may be configured to support one-way or two-way videotransmission to support applications such as video streaming, videoplayback, video broadcasting, and/or video telephony.

In the example of FIG. 1A, the source device 12 includes a video source18, a video encoder 20 and the output interface 22. In some cases, theoutput interface 22 may include a modulator/demodulator (modem) and/or atransmitter. In the source device 12, the video source 18 may include asource such as a video capture device, e.g., a video camera, a videoarchive containing previously captured video, a video feed interface toreceive video from a video content provider, and/or a computer graphicssystem for generating computer graphics data as the source video, or acombination of such sources. As one example, if the video source 18 is avideo camera, the source device 12 and the destination device 14 mayform so-called camera phones or video phones, as illustrated in theexample of FIG. 1B. However, the techniques described in this disclosuremay be applicable to video coding in general, and may be applied towireless and/or wired applications.

The captured, pre-captured, or computer-generated video may be encodedby video encoder 20. The encoded video data may be transmitted directlyto the destination device 14 via the output interface 22 of the sourcedevice 12. The encoded video data may also (or alternatively) be storedonto the storage device 31 for later access by the destination device 14or other devices, for decoding and/or playback. video encoder 20illustrated in FIGS. 1A and 1B may comprise video encoder 20 illustratedFIG. 2A, video encoder 23 illustrated in FIG. 2B, or any other videoencoder described herein.

In the example of FIG. 1A, the destination device 14 includes the inputinterface 28, a video decoder 30, and a display device 32. In somecases, the input interface 28 may include a receiver and/or a modem. Theinput interface 28 of the destination device 14 may receive the encodedvideo data over the link 16 and/or from the storage device 31. Theencoded video data communicated over the link 16, or provided on thestorage device 31, may include a variety of syntax elements generated byvideo encoder 20 for use by a video decoder, such as video decoder 30,in decoding the video data. Such syntax elements may be included withthe encoded video data transmitted on a communication medium, stored ona storage medium, or stored on a file server. Video decoder 30illustrated in FIGS. 1A and 1B may comprise video decoder 30 illustratedFIG. 3A, video decoder 33 illustrated in FIG. 3B, or any other videodecoder described herein.

The display device 32 may be integrated with, or external to, thedestination device 14. In some examples, the destination device 14 mayinclude an integrated display device and also be configured to interfacewith an external display device. In other examples, the destinationdevice 14 may be a display device. In general, the display device 32displays the decoded video data to a user, and may comprise any of avariety of display devices such as a liquid crystal display (LCD), aplasma display, an organic light emitting diode (OLED) display, oranother type of display device.

In related aspects, FIG. 1B shows an example video encoding and decodingsystem 10′ wherein the source and destination devices 12, 14 are on orpart of a device 11. The device 11 may be a telephone handset, such as a“smart” phone or the like. The device 11 may include an optionalprocessor/controller device 13 in operative communication with thesource and destination devices 12, 14. The system 10′ of FIG. 1B, andcomponents thereof, are otherwise similar to the system 10 of FIG. 1A,and components thereof.

Video encoder 20 and video decoder 30 may operate according to a videocompression standard, such as HEVC standard, and may conform to a HEVCTest Model (HM). Alternatively, video encoder 20 and video decoder 30may operate according to other proprietary or industry standards, suchas the ITU-T H.264 standard, alternatively referred to as MPEG-4, Part10, AVC, or extensions of such standards. The techniques of thisdisclosure, however, are not limited to any particular coding standard.Other examples of video compression standards include MPEG-2 and ITU-TH.263.

Although not shown in the examples of FIGS. 1A and 1B, video encoder 20and video decoder 30 may each be integrated with an audio encoder anddecoder, and may include appropriate MUX-DEMUX units, or other hardwareand software, to handle encoding of both audio and video in a commondata stream or separate data streams. If applicable, in some examples,MUX-DEMUX units may conform to the ITU H.223 multiplexer protocol, orother protocols such as the user datagram protocol (UDP).

Video encoder 20 and video decoder 30 each may be implemented as any ofa variety of suitable encoder circuitry, such as one or moremicroprocessors, digital signal processors (DSPs), application specificintegrated circuits (ASICs), field programmable gate arrays (FPGAs),discrete logic, software, hardware, firmware or any combinationsthereof. When the techniques are implemented partially in software, adevice may store instructions for the software in a suitable,non-transitory computer-readable medium and execute the instructions inhardware using one or more processors to perform the techniques of thisdisclosure. Each of video encoder 20 and video decoder 30 may beincluded in one or more encoders or decoders, either of which may beintegrated as part of a combined encoder/decoder (e.g., codec) in arespective device.

Video Coding Process

As mentioned briefly above, video encoder 20 encodes video data. Thevideo data may comprise one or more pictures. Each of the pictures is astill image forming part of a video. In some instances, a picture may bereferred to as a video “frame.” When video encoder 20 encodes the videodata, video encoder 20 may generate a bitstream. The bitstream mayinclude a sequence of bits that form a coded representation of the videodata. The bitstream may include coded pictures and associated data. Acoded picture is a coded representation of a picture.

To generate the bitstream, video encoder 20 may perform encodingoperations on each picture in the video data. When video encoder 20performs encoding operations on the pictures, video encoder 20 maygenerate a series of coded pictures and associated data. The associateddata may include video parameter sets (VPSs), sequence parameter sets(SPSs), picture parameter sets (PPSs), adaptation parameter sets (APSs),and other syntax structures. An SPS may contain parameters applicable tozero or more sequences of pictures. A PPS may contain parametersapplicable to zero or more pictures. An APS may contain parametersapplicable to zero or more pictures. Parameters in an APS may beparameters that are more likely to change than parameters in a PPS.

To generate a coded picture, video encoder 20 may partition a pictureinto equally-sized video blocks. A video block may be a two-dimensionalarray of samples. Each of the video blocks is associated with atreeblock. In some instances, a treeblock may be referred to as alargest coding unit (LCU). The treeblocks of HEVC may be broadlyanalogous to the macroblocks of previous standards, such as H.264/AVC.However, a treeblock is not necessarily limited to a particular size andmay include one or more coding units (CUs). Video encoder 20 may usequadtree partitioning to partition the video blocks of treeblocks intovideo blocks associated with CUs, hence the name “treeblocks.”

In some examples, video encoder 20 may partition a picture into aplurality of slices. Each of the slices may include an integer number ofCUs. In some instances, a slice comprises an integer number oftreeblocks. In other instances, a boundary of a slice may be within atreeblock.

As part of performing an encoding operation on a picture, video encoder20 may perform encoding operations on each slice of the picture. Whenvideo encoder 20 performs an encoding operation on a slice, videoencoder 20 may generate encoded data associated with the slice. Theencoded data associated with the slice may be referred to as a “codedslice.”

To generate a coded slice, video encoder 20 may perform encodingoperations on each treeblock in a slice. When video encoder 20 performsan encoding operation on a treeblock, video encoder 20 may generate acoded treeblock. The coded treeblock may comprise data representing anencoded version of the treeblock.

When video encoder 20 generates a coded slice, video encoder 20 mayperform encoding operations on (e.g., encode) the treeblocks in theslice according to a raster scan order. For example, video encoder 20may encode the treeblocks of the slice in an order that proceeds fromleft to right across a topmost row of treeblocks in the slice, then fromleft to right across a next lower row of treeblocks, and so on untilvideo encoder 20 has encoded each of the treeblocks in the slice.

As a result of encoding the treeblocks according to the raster scanorder, the treeblocks above and to the left of a given treeblock mayhave been encoded, but treeblocks below and to the right of the giventreeblock have not yet been encoded. Consequently, video encoder 20 maybe able to access information generated by encoding treeblocks above andto the left of the given treeblock when encoding the given treeblock.However, video encoder 20 may be unable to access information generatedby encoding treeblocks below and to the right of the given treeblockwhen encoding the given treeblock.

To generate a coded treeblock, video encoder 20 may recursively performquadtree partitioning on the video block of the treeblock to divide thevideo block into progressively smaller video blocks. Each of the smallervideo blocks may be associated with a different CU. For example, videoencoder 20 may partition the video block of a treeblock into fourequally-sized sub-blocks, partition one or more of the sub-blocks intofour equally-sized sub-sub-blocks, and so on. A partitioned CU may be aCU whose video block is partitioned into video blocks associated withother CUs. A non-partitioned CU may be a CU whose video block is notpartitioned into video blocks associated with other CUs.

One or more syntax elements in the bitstream may indicate a maximumnumber of times video encoder 20 may partition the video block of atreeblock. A video block of a CU may be square in shape. The size of thevideo block of a CU (e.g., the size of the CU) may range from 8×8 pixelsup to the size of a video block of a treeblock (e.g., the size of thetreeblock) with a maximum of 64×64 pixels or greater.

Video encoder 20 may perform encoding operations on (e.g., encode) eachCU of a treeblock according to a z-scan order. In other words, videoencoder 20 may encode a top-left CU, a top-right CU, a bottom-left CU,and then a bottom-right CU, in that order. When video encoder 20performs an encoding operation on a partitioned CU, video encoder 20 mayencode CUs associated with sub-blocks of the video block of thepartitioned CU according to the z-scan order. In other words, videoencoder 20 may encode a CU associated with a top-left sub-block, a CUassociated with a top-right sub-block, a CU associated with abottom-left sub-block, and then a CU associated with a bottom-rightsub-block, in that order.

As a result of encoding the CUs of a treeblock according to a z-scanorder, the CUs above, above-and-to-the-left, above-and-to-the-right,left, and below-and-to-the left of a given CU may have been encoded. CUsbelow and to the right of the given CU have not yet been encoded.Consequently, video encoder 20 may be able to access informationgenerated by encoding some CUs that neighbor the given CU when encodingthe given CU. However, video encoder 20 may be unable to accessinformation generated by encoding other CUs that neighbor the given CUwhen encoding the given CU.

When video encoder 20 encodes a non-partitioned CU, video encoder 20 maygenerate one or more prediction units (PUs) for the CU. Each of the PUsof the CU may be associated with a different video block within thevideo block of the CU. Video encoder 20 may generate a predicted videoblock for each PU of the CU. The predicted video block of a PU may be ablock of samples. Video encoder 20 may use intra prediction or interprediction to generate the predicted video block for a PU.

When video encoder 20 uses intra prediction to generate the predictedvideo block of a PU, video encoder 20 may generate the predicted videoblock of the PU based on decoded samples of the picture associated withthe PU. If video encoder 20 uses intra prediction to generate predictedvideo blocks of the PUs of a CU, the CU is an intra-predicted CU. Whenvideo encoder 20 uses inter prediction to generate the predicted videoblock of the PU, video encoder 20 may generate the predicted video blockof the PU based on decoded samples of one or more pictures other thanthe picture associated with the PU. If video encoder 20 uses interprediction to generate predicted video blocks of the PUs of a CU, the CUis an inter-predicted CU.

Furthermore, when video encoder 20 uses inter prediction to generate apredicted video block for a PU, video encoder 20 may generate motioninformation for the PU. The motion information for a PU may indicate oneor more reference blocks of the PU. Each reference block of the PU maybe a video block within a reference picture. The reference picture maybe a picture other than the picture associated with the PU. In someinstances, a reference block of a PU may also be referred to as the“reference sample” of the PU. Video encoder 20 may generate thepredicted video block for the PU based on the reference blocks of thePU.

After video encoder 20 generates predicted video blocks for one or morePUs of a CU, video encoder 20 may generate residual data for the CUbased on the predicted video blocks for the PUs of the CU. The residualdata for the CU may indicate differences between samples in thepredicted video blocks for the PUs of the CU and the original videoblock of the CU.

Furthermore, as part of performing an encoding operation on anon-partitioned CU, video encoder 20 may perform recursive quadtreepartitioning on the residual data of the CU to partition the residualdata of the CU into one or more blocks of residual data (e.g., residualvideo blocks) associated with transform units (TUs) of the CU. Each TUof a CU may be associated with a different residual video block.

Video encoder 20 may apply one or more transforms to residual videoblocks associated with the TUs to generate transform coefficient blocks(e.g., blocks of transform coefficients) associated with the TUs.Conceptually, a transform coefficient block may be a two-dimensional(2D) matrix of transform coefficients.

After generating a transform coefficient block, video encoder 20 mayperform a quantization process on the transform coefficient block.Quantization generally refers to a process in which transformcoefficients are quantized to possibly reduce the amount of data used torepresent the transform coefficients, providing further compression. Thequantization process may reduce the bit depth associated with some orall of the transform coefficients. For example, an n-bit transformcoefficient may be rounded down to an m-bit transform coefficient duringquantization, where n is greater than m.

Video encoder 20 may associate each CU with a quantization parameter(QP) value. The QP value associated with a CU may determine how videoencoder 20 quantizes transform coefficient blocks associated with theCU. Video encoder 20 may adjust the degree of quantization applied tothe transform coefficient blocks associated with a CU by adjusting theQP value associated with the CU.

After video encoder 20 quantizes a transform coefficient block, videoencoder 20 may generate sets of syntax elements that represent thetransform coefficients in the quantized transform coefficient block.Video encoder 20 may apply entropy encoding operations, such as ContextAdaptive Binary Arithmetic Coding (CABAC) operations, to some of thesesyntax elements. Other entropy coding techniques such as contextadaptive variable length coding (CAVLC), probability intervalpartitioning entropy (PIPE) coding, or other binary arithmetic codingcould also be used.

The bitstream generated by video encoder 20 may include a series ofNetwork Abstraction Layer (NAL) units. Each of the NAL units may be asyntax structure containing an indication of a type of data in the NALunit and bytes containing the data. For example, a NAL unit may containdata representing a video parameter set, a sequence parameter set, apicture parameter set, a coded slice, supplemental enhancementinformation (SEI), an access unit delimiter, filler data, or anothertype of data. The data in a NAL unit may include various syntaxstructures.

Video decoder 30 may receive the bitstream generated by video encoder20. The bitstream may include a coded representation of the video dataencoded by video encoder 20. When video decoder 30 receives thebitstream, video decoder 30 may perform a parsing operation on thebitstream. When video decoder 30 performs the parsing operation, videodecoder 30 may extract syntax elements from the bitstream. Video decoder30 may reconstruct the pictures of the video data based on the syntaxelements extracted from the bitstream. The process to reconstruct thevideo data based on the syntax elements may be generally reciprocal tothe process performed by video encoder 20 to generate the syntaxelements.

After video decoder 30 extracts the syntax elements associated with aCU, video decoder 30 may generate predicted video blocks for the PUs ofthe CU based on the syntax elements. In addition, video decoder 30 mayinverse quantize transform coefficient blocks associated with TUs of theCU. Video decoder 30 may perform inverse transforms on the transformcoefficient blocks to reconstruct residual video blocks associated withthe TUs of the CU. After generating the predicted video blocks andreconstructing the residual video blocks, video decoder 30 mayreconstruct the video block of the CU based on the predicted videoblocks and the residual video blocks. In this way, video decoder 30 mayreconstruct the video blocks of CUs based on the syntax elements in thebitstream.

Video Encoder

FIG. 2A is a block diagram illustrating an example of a video encoderthat may implement techniques in accordance with aspects described inthis disclosure. Video encoder 20 may be configured to process a singlelayer of a video frame, such as for HEVC. Further, video encoder 20 maybe configured to perform any or all of the techniques of thisdisclosure. As one example, prediction processing unit 100 may beconfigured to perform any or all of the techniques described in thisdisclosure. In another embodiment, video encoder 20 includes an optionalinter-layer prediction unit 128 that is configured to perform any or allof the techniques described in this disclosure. In other embodiments,inter-layer prediction can be performed by prediction processing unit100 (e.g., inter prediction unit 121 and/or intra prediction unit 126),in which case the inter-layer prediction unit 128 may be omitted.However, aspects of this disclosure are not so limited. In someexamples, the techniques described in this disclosure may be sharedamong the various components of video encoder 20. In some examples,additionally or alternatively, a processor (not shown) may be configuredto perform any or all of the techniques described in this disclosure.

For purposes of explanation, this disclosure describes video encoder 20in the context of HEVC coding. However, the techniques of thisdisclosure may be applicable to other coding standards or methods. Theexample depicted in FIG. 2A is for a single layer codec. However, aswill be described further with respect to FIG. 2B, some or all of videoencoder 20 may be duplicated for processing of a multi-layer codec.

Video encoder 20 may perform intra- and inter-coding of video blockswithin video slices. Intra coding relies on spatial prediction to reduceor remove spatial redundancy in video within a given video frame orpicture. Inter-coding relies on temporal prediction to reduce or removetemporal redundancy in video within adjacent frames or pictures of avideo sequence. Intra-mode (I mode) may refer to any of several spatialbased coding modes. Inter-modes, such as uni-directional prediction (Pmode) or bi-directional prediction (B mode), may refer to any of severaltemporal-based coding modes.

In the example of FIG. 2A, video encoder 20 includes a plurality offunctional components. The functional components of video encoder 20include a prediction processing unit 100, a residual generation unit102, a transform processing unit 104, a quantization unit 106, aninverse quantization unit 108, an inverse transform unit 110, areconstruction unit 112, a filter unit 113, a decoded picture buffer114, and an entropy encoding unit 116. Prediction processing unit 100includes an inter prediction unit 121, a motion estimation unit 122, amotion compensation unit 124, an intra prediction unit 126, and aninter-layer prediction unit 128. In other examples, video encoder 20 mayinclude more, fewer, or different functional components. Furthermore,motion estimation unit 122 and motion compensation unit 124 may behighly integrated, but are represented in the example of FIG. 2Aseparately for purposes of explanation.

Video encoder 20 may receive video data. Video encoder 20 may receivethe video data from various sources. For example, video encoder 20 mayreceive the video data from video source 18 (e.g., shown in FIG. 1A or1B) or another source. The video data may represent a series ofpictures. To encode the video data, video encoder 20 may perform anencoding operation on each of the pictures. As part of performing theencoding operation on a picture, video encoder 20 may perform encodingoperations on each slice of the picture. As part of performing anencoding operation on a slice, video encoder 20 may perform encodingoperations on treeblocks in the slice.

As part of performing an encoding operation on a treeblock, predictionprocessing unit 100 may perform quadtree partitioning on the video blockof the treeblock to divide the video block into progressively smallervideo blocks. Each of the smaller video blocks may be associated with adifferent CU. For example, prediction processing unit 100 may partitiona video block of a treeblock into four equally-sized sub-blocks,partition one or more of the sub-blocks into four equally-sizedsub-sub-blocks, and so on.

The sizes of the video blocks associated with CUs may range from 8×8samples up to the size of the treeblock with a maximum of 64×64 samplesor greater. In this disclosure, “N×N” and “N by N” may be usedinterchangeably to refer to the sample dimensions of a video block interms of vertical and horizontal dimensions, e.g., 16×16 samples or 16by 16 samples. In general, a 16×16 video block has sixteen samples in avertical direction (y=16) and sixteen samples in a horizontal direction(x=16) Likewise, an N×N block generally has N samples in a verticaldirection and N samples in a horizontal direction, where N represents anonnegative integer value.

Furthermore, as part of performing the encoding operation on atreeblock, prediction processing unit 100 may generate a hierarchicalquadtree data structure for the treeblock. For example, a treeblock maycorrespond to a root node of the quadtree data structure. If predictionprocessing unit 100 partitions the video block of the treeblock intofour sub-blocks, the root node has four child nodes in the quadtree datastructure. Each of the child nodes corresponds to a CU associated withone of the sub-blocks. If prediction processing unit 100 partitions oneof the sub-blocks into four sub-sub-blocks, the node corresponding tothe CU associated with the sub-block may have four child nodes, each ofwhich corresponds to a CU associated with one of the sub-sub-blocks.

Each node of the quadtree data structure may contain syntax data (e.g.,syntax elements) for the corresponding treeblock or CU. For example, anode in the quadtree may include a split flag that indicates whether thevideo block of the CU corresponding to the node is partitioned (e.g.,split) into four sub-blocks. Syntax elements for a CU may be definedrecursively, and may depend on whether the video block of the CU issplit into sub-blocks. A CU whose video block is not partitioned maycorrespond to a leaf node in the quadtree data structure. A codedtreeblock may include data based on the quadtree data structure for acorresponding treeblock.

Video encoder 20 may perform encoding operations on each non-partitionedCU of a treeblock. When video encoder 20 performs an encoding operationon a non-partitioned CU, video encoder 20 generates data representing anencoded representation of the non-partitioned CU.

As part of performing an encoding operation on a CU, predictionprocessing unit 100 may partition the video block of the CU among one ormore PUs of the CU. Video encoder 20 and video decoder 30 may supportvarious PU sizes. Assuming that the size of a particular CU is 2N×2N,video encoder 20 and video decoder 30 may support PU sizes of 2N×2N orN×N, and inter-prediction in symmetric PU sizes of 2N×2N, 2N×N, N×2N,N×N, 2N×nU, nL×2N, nR×2N, or similar. Video encoder 20 and video decoder30 may also support asymmetric partitioning for PU sizes of 2N×nU,2N×nD, nL×2N, and nR×2N. In some examples, prediction processing unit100 may perform geometric partitioning to partition the video block of aCU among PUs of the CU along a boundary that does not meet the sides ofthe video block of the CU at right angles.

Inter prediction unit 121 may perform inter prediction on each PU of theCU. Inter prediction may provide temporal compression. To perform interprediction on a PU, motion estimation unit 122 may generate motioninformation for the PU. Motion compensation unit 124 may generate apredicted video block for the PU based the motion information anddecoded samples of pictures other than the picture associated with theCU (e.g., reference pictures). In this disclosure, a predicted videoblock generated by motion compensation unit 124 may be referred to as aninter-predicted video block.

Slices may be I slices, P slices, or B slices. Motion estimation unit122 and motion compensation unit 124 may perform different operationsfor a PU of a CU depending on whether the PU is in an I slice, a Pslice, or a B slice. In an I slice, all PUs are intra predicted. Hence,if the PU is in an I slice, motion estimation unit 122 and motioncompensation unit 124 do not perform inter prediction on the PU.

If the PU is in a P slice, the picture containing the PU is associatedwith a list of reference pictures referred to as “list 0.” Each of thereference pictures in list 0 contains samples that may be used for interprediction of other pictures. When motion estimation unit 122 performsthe motion estimation operation with regard to a PU in a P slice, motionestimation unit 122 may search the reference pictures in list 0 for areference block for the PU. The reference block of the PU may be a setof samples, e.g., a block of samples, that most closely corresponds tothe samples in the video block of the PU. Motion estimation unit 122 mayuse a variety of metrics to determine how closely a set of samples in areference picture corresponds to the samples in the video block of a PU.For example, motion estimation unit 122 may determine how closely a setof samples in a reference picture corresponds to the samples in thevideo block of a PU by sum of absolute difference (SAD), sum of squareddifferences (SSD), or other difference metrics.

After identifying a reference block of a PU in a P slice, motionestimation unit 122 may generate a reference index that indicates thereference picture in list 0 containing the reference block and a motionvector that indicates a spatial displacement between the PU and thereference block. In various examples, motion estimation unit 122 maygenerate motion vectors to varying degrees of precision. For example,motion estimation unit 122 may generate motion vectors at one-quartersample precision, one-eighth sample precision, or other fractionalsample precision. In the case of fractional sample precision, referenceblock values may be interpolated from integer-position sample values inthe reference picture. Motion estimation unit 122 may output thereference index and the motion vector as the motion information of thePU. Motion compensation unit 124 may generate a predicted video block ofthe PU based on the reference block identified by the motion informationof the PU.

If the PU is in a B slice, the picture containing the PU may beassociated with two lists of reference pictures, referred to as “list 0”and “list 1.” In some examples, a picture containing a B slice may beassociated with a list combination that is a combination of list 0 andlist 1.

Furthermore, if the PU is in a B slice, motion estimation unit 122 mayperform uni-directional prediction or bi-directional prediction for thePU. When motion estimation unit 122 performs uni-directional predictionfor the PU, motion estimation unit 122 may search the reference picturesof list 0 or list 1 for a reference block for the PU. Motion estimationunit 122 may then generate a reference index that indicates thereference picture in list 0 or list 1 that contains the reference blockand a motion vector that indicates a spatial displacement between the PUand the reference block. Motion estimation unit 122 may output thereference index, a prediction direction indicator, and the motion vectoras the motion information of the PU. The prediction direction indicatormay indicate whether the reference index indicates a reference picturein list 0 or list 1. Motion compensation unit 124 may generate thepredicted video block of the PU based on the reference block indicatedby the motion information of the PU.

When motion estimation unit 122 performs bi-directional prediction for aPU, motion estimation unit 122 may search the reference pictures in list0 for a reference block for the PU and may also search the referencepictures in list 1 for another reference block for the PU. Motionestimation unit 122 may then generate reference indexes that indicatethe reference pictures in list 0 and list 1 containing the referenceblocks and motion vectors that indicate spatial displacements betweenthe reference blocks and the PU. Motion estimation unit 122 may outputthe reference indexes and the motion vectors of the PU as the motioninformation of the PU. Motion compensation unit 124 may generate thepredicted video block of the PU based on the reference blocks indicatedby the motion information of the PU.

In some instances, motion estimation unit 122 does not output a full setof motion information for a PU to entropy encoding unit 116. Rather,motion estimation unit 122 may signal the motion information of a PUwith reference to the motion information of another PU. For example,motion estimation unit 122 may determine that the motion information ofthe PU is sufficiently similar to the motion information of aneighboring PU. In this example, motion estimation unit 122 mayindicate, in a syntax structure associated with the PU, a value thatindicates to video decoder 30 that the PU has the same motioninformation as the neighboring PU. In another example, motion estimationunit 122 may identify, in a syntax structure associated with the PU, aneighboring PU and a motion vector difference (MVD). The motion vectordifference indicates a difference between the motion vector of the PUand the motion vector of the indicated neighboring PU. Video decoder 30may use the motion vector of the indicated neighboring PU and the motionvector difference to determine the motion vector of the PU. By referringto the motion information of a first PU when signaling the motioninformation of a second PU, video encoder 20 may be able to signal themotion information of the second PU using fewer bits.

As part of performing an encoding operation on a CU, intra predictionunit 126 may perform intra prediction on PUs of the CU. Intra predictionmay provide spatial compression. When intra prediction unit 126 performsintra prediction on a PU, intra prediction unit 126 may generateprediction data for the PU based on decoded samples of other PUs in thesame picture. The prediction data for the PU may include a predictedvideo block and various syntax elements. Intra prediction unit 126 mayperform intra prediction on PUs in I slices, P slices, and B slices.

To perform intra prediction on a PU, intra prediction unit 126 may usemultiple intra prediction modes to generate multiple sets of predictiondata for the PU. When intra prediction unit 126 uses an intra predictionmode to generate a set of prediction data for the PU, intra predictionunit 126 may extend samples from video blocks of neighboring PUs acrossthe video block of the PU in a direction and/or gradient associated withthe intra prediction mode. The neighboring PUs may be above, above andto the right, above and to the left, or to the left of the PU, assuminga left-to-right, top-to-bottom encoding order for PUs, CUs, andtreeblocks. Intra prediction unit 126 may use various numbers of intraprediction modes, e.g., 33 directional intra prediction modes, dependingon the size of the PU.

Prediction processing unit 100 may select the prediction data for a PUfrom among the prediction data generated by motion compensation unit 124for the PU or the prediction data generated by intra prediction unit 126for the PU. In some examples, prediction processing unit 100 selects theprediction data for the PU based on rate/distortion metrics of the setsof prediction data.

If prediction processing unit 100 selects prediction data generated byintra prediction unit 126, prediction processing unit 100 may signal theintra prediction mode that was used to generate the prediction data forthe PUs, e.g., the selected intra prediction mode. Prediction processingunit 100 may signal the selected intra prediction mode in various ways.For example, it may be probable that the selected intra prediction modeis the same as the intra prediction mode of a neighboring PU. In otherwords, the intra prediction mode of the neighboring PU may be the mostprobable mode for the current PU. Thus, prediction processing unit 100may generate a syntax element to indicate that the selected intraprediction mode is the same as the intra prediction mode of theneighboring PU.

As discussed above, video encoder 20 may include inter-layer predictionunit 128. Inter-layer prediction unit 128 is configured to predict acurrent block (e.g., a current block in the EL) using one or moredifferent layers that are available in SVC (e.g., a BL or RL). Suchprediction may be referred to as inter-layer prediction. Inter-layerprediction unit 128 utilizes prediction methods to reduce inter-layerredundancy, thereby improving coding efficiency and reducingcomputational resource requirements. Some examples of inter-layerprediction include inter-layer intra prediction, inter-layer motionprediction, and inter-layer residual prediction. Inter-layer intraprediction uses the reconstruction of co-located blocks in the BL topredict the current block in the EL. Inter-layer motion prediction usesmotion information of the BL to predict motion in the EL. Inter-layerresidual prediction uses the residue of the BL to predict the residue ofthe EL. Each of the inter-layer prediction schemes is discussed below ingreater detail.

After prediction processing unit 100 selects the prediction data for PUsof a CU, residual generation unit 102 may generate residual data for theCU by subtracting (e.g., indicated by the minus sign) the predictedvideo blocks of the PUs of the CU from the video block of the CU. Theresidual data of a CU may include 2D residual video blocks thatcorrespond to different sample components of the samples in the videoblock of the CU. For example, the residual data may include a residualvideo block that corresponds to differences between luminance componentsof samples in the predicted video blocks of the PUs of the CU andluminance components of samples in the original video block of the CU.In addition, the residual data of the CU may include residual videoblocks that correspond to the differences between chrominance componentsof samples in the predicted video blocks of the PUs of the CU and thechrominance components of the samples in the original video block of theCU.

Prediction processing unit 100 may perform quadtree partitioning topartition the residual video blocks of a CU into sub-blocks. Eachundivided residual video block may be associated with a different TU ofthe CU. The sizes and positions of the residual video blocks associatedwith TUs of a CU may or may not be based on the sizes and positions ofvideo blocks associated with the PUs of the CU. A quadtree structureknown as a “residual quad tree” (RQT) may include nodes associated witheach of the residual video blocks. The TUs of a CU may correspond toleaf nodes of the RQT.

Transform processing unit 104 may generate one or more transformcoefficient blocks for each TU of a CU by applying one or moretransforms to a residual video block associated with the TU. Each of thetransform coefficient blocks may be a 2D matrix of transformcoefficients. Transform processing unit 104 may apply various transformsto the residual video block associated with a TU. For example, transformprocessing unit 104 may apply a discrete cosine transform (DCT), adirectional transform, or a conceptually similar transform to theresidual video block associated with a TU.

After transform processing unit 104 generates a transform coefficientblock associated with a TU, quantization unit 106 may quantize thetransform coefficients in the transform coefficient block. Quantizationunit 106 may quantize a transform coefficient block associated with a TUof a CU based on a QP value associated with the CU.

Video encoder 20 may associate a QP value with a CU in various ways. Forexample, video encoder 20 may perform a rate-distortion analysis on atreeblock associated with the CU. In the rate-distortion analysis, videoencoder 20 may generate multiple coded representations of the treeblockby performing an encoding operation multiple times on the treeblock.Video encoder 20 may associate different QP values with the CU whenvideo encoder 20 generates different encoded representations of thetreeblock. Video encoder 20 may signal that a given QP value isassociated with the CU when the given QP value is associated with the CUin a coded representation of the treeblock that has a lowest bitrate anddistortion metric.

Inverse quantization unit 108 and inverse transform unit 110 may applyinverse quantization and inverse transforms to the transform coefficientblock, respectively, to reconstruct a residual video block from thetransform coefficient block. Reconstruction unit 112 may add thereconstructed residual video block to corresponding samples from one ormore predicted video blocks generated by prediction processing unit 100to produce a reconstructed video block associated with a TU. Byreconstructing video blocks for each TU of a CU in this way, videoencoder 20 may reconstruct the video block of the CU.

After reconstruction unit 112 reconstructs the video block of a CU,filter unit 113 may perform a deblocking operation to reduce blockingartifacts in the video block associated with the CU. After performingthe one or more deblocking operations, filter unit 113 may store thereconstructed video block of the CU in decoded picture buffer 114.Motion estimation unit 122 and motion compensation unit 124 may use areference picture that contains the reconstructed video block to performinter prediction on PUs of subsequent pictures. In addition, intraprediction unit 126 may use reconstructed video blocks in decodedpicture buffer 114 to perform intra prediction on other PUs in the samepicture as the CU.

Entropy encoding unit 116 may receive data from other functionalcomponents of video encoder 20. For example, entropy encoding unit 116may receive transform coefficient blocks from quantization unit 106 andmay receive syntax elements from prediction processing unit 100. Whenentropy encoding unit 116 receives the data, entropy encoding unit 116may perform one or more entropy encoding operations to generate entropyencoded data. For example, video encoder 20 may perform a CAVLCoperation, a CABAC operation, a variable-to-variable (V2V) length codingoperation, a syntax-based context-adaptive binary arithmetic coding(SBAC) operation, a Probability Interval Partitioning Entropy (PIPE)coding operation, or another type of entropy encoding operation on thedata. Entropy encoding unit 116 may output a bitstream that includes theentropy encoded data.

As part of performing an entropy encoding operation on data, entropyencoding unit 116 may select a context model. If entropy encoding unit116 is performing a CABAC operation, the context model may indicateestimates of probabilities of particular bins having particular values.In the context of CABAC, the term “bin” is used to refer to a bit of abinarized version of a syntax element.

Multi-Layer Video Encoder

FIG. 2B is a block diagram illustrating an example of a multi-layervideo encoder 23 (also simply referred to as video encoder 23) that mayimplement techniques in accordance with aspects described in thisdisclosure. Video encoder 23 may be configured to process multi-layervideo frames, such as for SHVC and multiview coding. Further, videoencoder 23 may be configured to perform any or all of the techniques ofthis disclosure.

Video encoder 23 includes a video encoder 20A and video encoder 20B,each of which may be configured as video encoder 20 and may perform thefunctions described above with respect to video encoder 20. Further, asindicated by the reuse of reference numbers, video encoders 20A and 20Bmay include at least some of the systems and subsystems as video encoder20. Although video encoder 23 is illustrated as including two videoencoders 20A and 20B, video encoder 23 is not limited as such and mayinclude any number of video encoder 20 layers. In some embodiments,video encoder 23 may include a video encoder 20 for each picture orframe in an access unit. For example, an access unit that includes fivepictures may be processed or encoded by a video encoder that includesfive encoder layers. In some embodiments, video encoder 23 may includemore encoder layers than frames in an access unit. In some such cases,some of the video encoder layers may be inactive when processing someaccess units.

In addition to video encoders 20A and 20B, video encoder 23 may includea resampling unit 90. The resampling unit 90 may, in some cases,upsample a BL of a received video frame to, for example, create an EL.The resampling unit 90 may upsample particular information associatedwith the received BL of a frame, but not other information. For example,the resampling unit 90 may upsample the spatial size or number of pixelsof the BL, but the number of slices or the picture order count mayremain constant. In some cases, the resampling unit 90 may not processthe received video and/or may be optional. For example, in some cases,the prediction processing unit 100 may perform upsampling. In someembodiments, the resampling unit 90 is configured to upsample a layerand reorganize, redefine, modify, or adjust one or more slices to complywith a set of slice boundary rules and/or raster scan rules. Althoughprimarily described as upsampling a BL, or a lower layer in an accessunit, in some cases, the resampling unit 90 may downsample a layer. Forexample, if during streaming of a video bandwidth is reduced, a framemay be downsampled instead of upsampled.

The resampling unit 90 may be configured to receive a picture or frame(or picture information associated with the picture) from the decodedpicture buffer 114 of the lower layer encoder (e.g., video encoder 20A)and to upsample the picture (or the received picture information). Thisupsampled picture may then be provided to the prediction processing unit100 of a higher layer encoder (e.g., video encoder 20B) configured toencode a picture in the same access unit as the lower layer encoder. Insome cases, the higher layer encoder is one layer removed from the lowerlayer encoder. In other cases, there may be one or more higher layerencoders between the layer 0 video encoder and the layer 1 encoder ofFIG. 2B.

In some cases, the resampling unit 90 may be omitted or bypassed. Insuch cases, the picture from the decoded picture buffer 114 of videoencoder 20A may be provided directly, or at least without being providedto the resampling unit 90, to the prediction processing unit 100 ofvideo encoder 20B. For example, if video data provided to video encoder20B and the reference picture from the decoded picture buffer 114 ofvideo encoder 20A are of the same size or resolution, the referencepicture may be provided to video encoder 20B without any resampling.

In some embodiments, video encoder 23 downsamples video data to beprovided to the lower layer encoder using the downsampling unit 94before provided the video data to video encoder 20A. Alternatively, thedownsampling unit 94 may be a resampling unit 90 capable of upsamplingor downsampling the video data. In yet other embodiments, thedownsampling unit 94 may be omitted.

As illustrated in FIG. 2B, video encoder 23 may further include amultiplexor 98, or mux. The mux 98 can output a combined bitstream fromvideo encoder 23. The combined bitstream may be created by taking abitstream from each of video encoders 20A and 20B and alternating whichbitstream is output at a given time. While in some cases the bits fromthe two (or more in the case of more than two video encoder layers)bitstreams may be alternated one bit at a time, in many cases thebitstreams are combined differently. For example, the output bitstreammay be created by alternating the selected bitstream one block at atime. In another example, the output bitstream may be created byoutputting a non-1:1 ratio of blocks from each of video encoders 20A and20B. For instance, two blocks may be output from video encoder 20B foreach block output from video encoder 20A. In some embodiments, theoutput stream from the mux 98 may be preprogrammed. In otherembodiments, the mux 98 may combine the bitstreams from video encoders20A, 20B based on a control signal received from a system external tovideo encoder 23, such as from a processor on a source device includingthe source device 12. The control signal may be generated based on theresolution or bitrate of a video from the video source 18, based on abandwidth of the link 16, based on a subscription associated with a user(e.g., a paid subscription versus a free subscription), or based on anyother factor for determining a resolution output desired from videoencoder 23.

Video Decoder

FIG. 3A is a block diagram illustrating an example of a video decoderthat may implement techniques in accordance with aspects described inthis disclosure. Video decoder 30 may be configured to process a singlelayer of a video frame, such as for HEVC. Further, video decoder 30 maybe configured to perform any or all of the techniques of thisdisclosure. As one example, motion compensation unit 162 and/or intraprediction unit 164 may be configured to perform any or all of thetechniques described in this disclosure. In one embodiment, videodecoder 30 may optionally include inter-layer prediction unit 166 thatis configured to perform any or all of the techniques described in thisdisclosure. In other embodiments, inter-layer prediction can beperformed by prediction processing unit 152 (e.g., motion compensationunit 162 and/or intra prediction unit 164), in which case theinter-layer prediction unit 166 may be omitted. However, aspects of thisdisclosure are not so limited. In some examples, the techniquesdescribed in this disclosure may be shared among the various componentsof video decoder 30. In some examples, additionally or alternatively, aprocessor (not shown) may be configured to perform any or all of thetechniques described in this disclosure.

For purposes of explanation, this disclosure describes video decoder 30in the context of HEVC coding. However, the techniques of thisdisclosure may be applicable to other coding standards or methods. Theexample depicted in FIG. 3A is for a single layer codec. However, aswill be described further with respect to FIG. 3B, some or all of videodecoder 30 may be duplicated for processing of a multi-layer codec.

In the example of FIG. 3A, video decoder 30 includes a plurality offunctional components. The functional components of video decoder 30include an entropy decoding unit 150, a prediction processing unit 152,an inverse quantization unit 154, an inverse transform unit 156, areconstruction unit 158, a filter unit 159, and a decoded picture buffer160. Prediction processing unit 152 includes a motion compensation unit162, an intra prediction unit 164, and an inter-layer prediction unit166. In some examples, video decoder 30 may perform a decoding passgenerally reciprocal to the encoding pass described with respect tovideo encoder 20 of FIG. 2A. In other examples, video decoder 30 mayinclude more, fewer, or different functional components.

Video decoder 30 may receive a bitstream that comprises encoded videodata. The bitstream may include a plurality of syntax elements. Whenvideo decoder 30 receives the bitstream, entropy decoding unit 150 mayperform a parsing operation on the bitstream. As a result of performingthe parsing operation on the bitstream, entropy decoding unit 150 mayextract syntax elements from the bitstream. As part of performing theparsing operation, entropy decoding unit 150 may entropy decode entropyencoded syntax elements in the bitstream. Prediction processing unit152, inverse quantization unit 154, inverse transform unit 156,reconstruction unit 158, and filter unit 159 may perform areconstruction operation that generates decoded video data based on thesyntax elements extracted from the bitstream.

As discussed above, the bitstream may comprise a series of NAL units.The NAL units of the bitstream may include video parameter set NALunits, sequence parameter set NAL units, picture parameter set NALunits, SEI NAL units, and so on. As part of performing the parsingoperation on the bitstream, entropy decoding unit 150 may performparsing operations that extract and entropy decode sequence parametersets from sequence parameter set NAL units, picture parameter sets frompicture parameter set NAL units, SEI data from SEI NAL units, and so on.

In addition, the NAL units of the bitstream may include coded slice NALunits. As part of performing the parsing operation on the bitstream,entropy decoding unit 150 may perform parsing operations that extractand entropy decode coded slices from the coded slice NAL units. Each ofthe coded slices may include a slice header and slice data. The sliceheader may contain syntax elements pertaining to a slice. The syntaxelements in the slice header may include a syntax element thatidentifies a picture parameter set associated with a picture thatcontains the slice. Entropy decoding unit 150 may perform entropydecoding operations, such as CABAC decoding operations, on syntaxelements in the coded slice header to recover the slice header.

As part of extracting the slice data from coded slice NAL units, entropydecoding unit 150 may perform parsing operations that extract syntaxelements from coded CUs in the slice data. The extracted syntax elementsmay include syntax elements associated with transform coefficientblocks. Entropy decoding unit 150 may then perform CABAC decodingoperations on some of the syntax elements.

After entropy decoding unit 150 performs a parsing operation on anon-partitioned CU, video decoder 30 may perform a reconstructionoperation on the non-partitioned CU. To perform the reconstructionoperation on a non-partitioned CU, video decoder 30 may perform areconstruction operation on each TU of the CU. By performing thereconstruction operation for each TU of the CU, video decoder 30 mayreconstruct a residual video block associated with the CU.

As part of performing a reconstruction operation on a TU, inversequantization unit 154 may inverse quantize, e.g., de-quantize, atransform coefficient block associated with the TU. Inverse quantizationunit 154 may inverse quantize the transform coefficient block in amanner similar to the inverse quantization processes proposed for HEVCor defined by the H.264 decoding standard. Inverse quantization unit 154may use a quantization parameter QP calculated by video encoder 20 for aCU of the transform coefficient block to determine a degree ofquantization and, likewise, a degree of inverse quantization for inversequantization unit 154 to apply.

After inverse quantization unit 154 inverse quantizes a transformcoefficient block, inverse transform unit 156 may generate a residualvideo block for the TU associated with the transform coefficient block.Inverse transform unit 156 may apply an inverse transform to thetransform coefficient block in order to generate the residual videoblock for the TU. For example, inverse transform unit 156 may apply aninverse DCT, an inverse integer transform, an inverse Karhunen-Loevetransform (KLT), an inverse rotational transform, an inverse directionaltransform, or another inverse transform to the transform coefficientblock. In some examples, inverse transform unit 156 may determine aninverse transform to apply to the transform coefficient block based onsignaling from video encoder 20. In such examples, inverse transformunit 156 may determine the inverse transform based on a signaledtransform at the root node of a quadtree for a treeblock associated withthe transform coefficient block. In other examples, inverse transformunit 156 may infer the inverse transform from one or more codingcharacteristics, such as block size, coding mode, or the like. In someexamples, inverse transform unit 156 may apply a cascaded inversetransform.

In some examples, motion compensation unit 162 may refine the predictedvideo block of a PU by performing interpolation based on interpolationfilters. Identifiers for interpolation filters to be used for motioncompensation with sub-sample precision may be included in the syntaxelements. Motion compensation unit 162 may use the same interpolationfilters used by video encoder 20 during generation of the predictedvideo block of the PU to calculate interpolated values for sub-integersamples of a reference block. Motion compensation unit 162 may determinethe interpolation filters used by video encoder 20 according to receivedsyntax information and use the interpolation filters to produce thepredicted video block.

Multi-Layer Decoder

FIG. 3B is a block diagram illustrating an example of a multi-layervideo decoder 33 (also simply referred to as video decoder 33) that mayimplement techniques in accordance with aspects described in thisdisclosure. The video decoder 33 may be configured to processmulti-layer video frames, such as for SHVC and multiview coding.Further, the video decoder 33 may be configured to perform any or all ofthe techniques of this disclosure.

The video decoder 33 includes a video decoder 30A and video decoder 30B,each of which may be configured as the video decoder 30 and may performthe functions described above with respect to the video decoder 30.Further, as indicated by the reuse of reference numbers, the videodecoders 30A and 30B may include at least some of the systems andsubsystems as the video decoder 30. Although the video decoder 33 isillustrated as including two video decoders 30A and 30B, the videodecoder 33 is not limited as such and may include any number of videodecoder 30 layers. In some embodiments, the video decoder 33 may includea video decoder 30 for each picture or frame in an access unit. Forexample, an access unit that includes five pictures may be processed ordecoded by a video decoder that includes five decoder layers. In someembodiments, the video decoder 33 may include more decoder layers thanframes in an access unit. In some such cases, some of the video decoderlayers may be inactive when processing some access units.

In addition to the video decoders 30A and 30B, the video decoder 33 mayinclude an upsampling unit 92. In some embodiments, the upsampling unit92 may upsample a base layer of a received video frame to create anenhanced layer to be added to the reference picture list for the frameor access unit. This enhanced layer can be stored in the decoded picturebuffer 160. In some embodiments, the upsampling unit 92 can include someor all of the embodiments described with respect to the resampling unit90 of FIG. 2A. In some embodiments, the upsampling unit 92 is configuredto upsample a layer and reorganize, redefine, modify, or adjust one ormore slices to comply with a set of slice boundary rules and/or rasterscan rules. In some cases, the upsampling unit 92 may be a resamplingunit configured to upsample and/or downsample a layer of a receivedvideo frame

The upsampling unit 92 may be configured to receive a picture or frame(or picture information associated with the picture) from the decodedpicture buffer 160 of the lower layer decoder (e.g., the video decoder30A) and to upsample the picture (or the received picture information).This upsampled picture may then be provided to the prediction processingunit 152 of a higher layer decoder (e.g., the video decoder 30B)configured to decode a picture in the same access unit as the lowerlayer decoder. In some cases, the higher layer decoder is one layerremoved from the lower layer decoder. In other cases, there may be oneor more higher layer decoders between the layer 0 decoder and the layer1 decoder of FIG. 3B.

In some cases, the upsampling unit 92 may be omitted or bypassed. Insuch cases, the picture from the decoded picture buffer 160 of the videodecoder 30A may be provided directly, or at least without being providedto the upsampling unit 92, to the prediction processing unit 152 of thevideo decoder 30B. For example, if video data provided to the videodecoder 30B and the reference picture from the decoded picture buffer160 of the video decoder 30A are of the same size or resolution, thereference picture may be provided to the video decoder 30B withoutupsampling. Further, in some embodiments, the upsampling unit 92 may bea resampling unit 90 configured to upsample or downsample a referencepicture received from the decoded picture buffer 160 of the videodecoder 30A.

As illustrated in FIG. 3B, the video decoder 33 may further include ademultiplexor (or demux) 99. The demux 99 can split an encoded videobitstream into multiple bitstreams with each bitstream output by thedemux 99 being provided to a different video decoder 30A and 30B. Themultiple bitstreams may be created by receiving a bitstream and each ofthe video decoders 30A and 30B receives a portion of the bitstream at agiven time. While in some cases the bits from the bitstream received atthe demux 99 may be alternated one bit at a time between each of thevideo decoders (e.g., video decoders 30A and 30B in the example of FIG.3B), in many cases the bitstream is divided differently. For example,the bitstream may be divided by alternating which video decoder receivesthe bitstream one block at a time. In another example, the bitstream maybe divided by a non-1:1 ratio of blocks to each of the video decoders30A and 30B. For instance, two blocks may be provided to the videodecoder 30B for each block provided to the video decoder 30A. In someembodiments, the division of the bitstream by the demux 99 may bepreprogrammed. In other embodiments, the demux 99 may divide thebitstream based on a control signal received from a system external tothe video decoder 33, such as from a processor on a destination deviceincluding the destination device 14. The control signal may be generatedbased on the resolution or bitrate of a video from the input interface28, based on a bandwidth of the link 16, based on a subscriptionassociated with a user (e.g., a paid subscription versus a freesubscription), or based on any other factor for determining a resolutionobtainable by the video decoder 33.

Scanning in HEVC

A scan pattern converts a 2-D block into a 1-D array and defines aprocessing order for the samples or coefficients. A scan pass is aniteration over the transform coefficients in a block (as per theselected scan pattern) in order to code a particular syntax element.

FIG. 4 is an illustration of exemplary scan patterns. In HEVC, the scanin a 4×4 Transform Block (TB) is diagonal as shown in block 405.However, horizontal scans as shown in block 410 and/or vertical scans asshown in block 415 may also be applied, as shown in the example intracase for 4×4 and 8×8 TBs.

HEVC utilizes a CG based transform coefficient coding scheme. A CG maybe a set of 16 consecutive transform coefficients in a scan order. Basedon the scan patterns defined in HEVC including diagonal, horizontal andvertical, a CG may also correspond to a 4×4 sub-block. This example isillustrated in FIG. 4, where each color/shading corresponds to adifferent CG. FIG. 4 shows an 8×8 transform block in HEVC having fourCGs. For a 4×4 transform block (TB), exactly one CG is included. For8×8, 16×16, 32×32 TBs, totally 4, 16 and 64 non-overlapping 4×4 CGs arepartitioned.

Prediction Types in HEVC

In HEVC, either an intra or inter prediction scheme may be used. HEVCprovides inter-picture prediction to exploit temporal statisticaldependences, intra-picture prediction to exploit spatial statisticaldependences, and transform coding of the prediction residual signals tofurther exploit spatial statistical dependences. HEVC supports variousintra-picture predictive coding methods based on different Intraprediction types (e.g., Intra_Angular, Intra_Planar, and Intra_DC(Direct Current)). For inter-picture prediction, HEVC allows twodifferent inter prediction types, including Advanced Motion VectorPrediction (AMVP) and Merge mode prediction.

Fast RDOQ

In HEVC, a video encoder 20 may perform quantization using RDOQ. RDOQ isa quantization technique that attempts to optimize the trade-offsbetween rate (i.e., the bit rate of encoded video data) and distortion.RDOQ may achieve significant performance gains over other quantizationtechniques. However, RDOQ is significantly more complex than, forexample, scalar quantization as well as other quantization techniques.

In general, a video encoder 20 may perform the RDOQ technique byperforming the following steps. First, video encoder 20 may initialize acontext. Second, video encoder 20 may scan through the coefficients ofthe coefficient block in reverse diagonal scan order. As video encoder20 scans each coefficient, video encoder 20 may use a quantizationoffset of ½ to quantize the coefficient. Third, video encoder 20 maydetermine optimal levels for coefficients in the coefficient block.Fourth, video encoder 20 may determine the optimal last significantcoefficient.

In HM, a coefficient block can be quantized with either RDOQ enabled ordisabled. When RDOQ is disabled, a conventional (i.e., non-RDOQ)quantization scheme is applied, and for each coefficient block, theresidual sample B_(ij), where B_(ij) means the transform coefficientlocated at coordinate (i, j) inside block B, is quantized as:

${= {{{sign}\left( B_{ij} \right)} \cdot \frac{{B_{ij}} + {f \cdot \Delta}}{\Delta}}},$where f is a constant value close to ⅓ for intra coded coefficientblocks and close to ⅙ for inter coded coefficient blocks, and Δrepresents the quantization step size.

When RDOQ is enabled, the residual block B is quantized using RDOQ. TheRDOQ process may involve, for each coefficient within each CG, applyingan initial quantization based on the above equation for {circumflex over(B)}_(i,j), above, with f equal to 0.5. This initial quantization isperformed in reverse scanning order. Rate-distortion (R-D) cost ofseveral quantization values, including Quantized Value (V), V−1 and 0,are compared. The quantization value with the lowest R-D cost isselected. In addition, the R-D cost of setting all the coefficients inthe current CG to 0 is calculated; if the R-D cost is smaller, then allcoefficients in the current CG are set to 0. Moreover, for eachquantized transform coefficient starting from the first nonzeroquantized coefficient in reverse scanning order, if the currentquantized transform coefficient is nonzero, the following are applied:if the R-D cost is reduced by setting the current quantized transformcoefficient as the last quantized coefficient, the last quantizedcoefficient is updated accordingly; and if the current last coefficientis larger than 1, the whole RDOQ process is terminated.

In HM, if RDOQ is enabled, it is performed for every coefficient blockgenerated by different coding process. Coding processes may include anIntra prediction type or an Inter prediction type, but are not limitedto a certain CU, PU, or TU partitioning type. Therefore, for each block,the above RDOQ process is generally performed multiple times.

RDOQ is an important encoder-side optimization method to achievesuperior video compression efficiency. However, compared to theconventional quantization scheme, the complexity of RDOQ is very highbecause much more complex computations are involved, and such complexcomputations are performed multiple times for each coefficient block.Due to the high complexity of RDOQ, its application may be limited in apractical video encoder, especially for real-time video encodingapplications.

To largely reduce the complexity of RDOQ while keeping the majority ofthe coding gain, a low-complexity RDOQ technique is described below.

In the original RDOQ implementation, RDOQ is performed multiple timesduring a decision process. However, it is noted that, the bestprediction type and/or partition type of each block is relatively stableno matter RDOQ is performed or not. It is proposed herein to excludeRDOQ during the decision process, and then after the best predictiontype and/or partition type has been determined or identified, to performRDOQ only on the best prediction type and/or partition type.

In one example, for the Intra prediction mode decision process in Intracoding, RDOQ is only applied for the best Intra prediction mode which isdetermined or decided without RDOQ. In another example, for the Mergemode decision process in Inter coding, RDOQ is only applied for the bestMerge mode which is determined without RDOQ.

FIG. 5 is a flowchart of an exemplary embodiment of a process forperforming RDOQ in accordance with aspect(s) described in thisdisclosure. The process 500 starts at block 505.

At block 510, the process 500 may involve performing a decision processfor a block of video data. For example, the decision process may provideinformation regarding how to efficiently encode the block of video data.In an embodiment, the mode decision process may involve applying atleast one prediction error criteria to the block of video data. Forexample, R-D, SAD, and/or SSD may be applied. This information may beused in determining one or more prediction and/or partition types foruse in the encoding process. In an embodiment, the determined one ormore prediction and/or partition types may be the types that are mostsuitable for the block of video data (e.g., the types having a lowestR-D, SAD, and/or SSD cost).

At block 515, the process 500 may involve applying a non-RDOQquantization scheme to the block of video data. The non-RDOQquantization scheme may be applied during the decision process. In analternative embodiment, multiple non-RDOQ quantization schemes may beapplied during the decision process.

At block 520, the process 500 may involve determining at least oneprediction type. For example, Merge modes, AMVP modes, and Intraprediction modes may be prediction types. The process 500 may determinea prediction type to use in encoding the block of video data. During thedecision process, the at least one prediction error criteria may beapplied to determine a suitable prediction type. For example, theprediction type having a lowest R-D cost may be selected.

At block 525, the process 500 may involve determining at least onepartition type. For example, CU, PU, and TU may be partition types.During the decision process, the at least one prediction error criteriamay be applied to determine a suitable partition type.

At block 530, the process 500 may involve applying RDOQ to the block ofvideo data. RDOQ may be applied after the decision process and/or upondetermining the at least one prediction type and/or partition type. Inan embodiment, RDOQ may be applied for only a best prediction and/orpartition type. In an alternative embodiment, RDOQ may be applied formultiple prediction and/or partition types to determine a bestprediction and/or partition type. The process 500 may end at block 535.

With the above proposed technique, only around 0.3% coding performancedrop is observed with 5%-25% (depending on quantization parameter andsequence) encoding time savings.

Other Considerations

Information and signals disclosed herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative logical blocks, modules, circuits, andalgorithm steps described in connection with the embodiments disclosedherein may be implemented as electronic hardware, computer software, orcombinations of both. To clearly illustrate this interchangeability ofhardware and software, various illustrative components, blocks, modules,circuits, and steps have been described above generally in terms oftheir functionality. Whether such functionality is implemented ashardware or software depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentinvention.

The techniques described herein may be implemented in hardware,software, firmware, or any combination thereof. Such techniques may beimplemented in any of a variety of devices such as general purposescomputers, wireless communication device handsets, or integrated circuitdevices having multiple uses including application in wirelesscommunication device handsets and other devices. Any features describedas modules or components may be implemented together in an integratedlogic device or separately as discrete but interoperable logic devices.If implemented in software, the techniques may be realized at least inpart by a computer-readable data storage medium comprising program codeincluding instructions that, when executed, performs one or more of themethods described above. The computer-readable data storage medium mayform part of a computer program product, which may include packagingmaterials. The computer-readable medium may comprise memory or datastorage media, such as random access memory (RAM) such as synchronousdynamic random access memory (SDRAM), read-only memory (ROM),non-volatile random access memory (NVRAM), electrically erasableprogrammable read-only memory (EEPROM), flash memory, magnetic oroptical data storage media, and the like. The techniques additionally,or alternatively, may be realized at least in part by acomputer-readable communication medium that carries or communicatesprogram code in the form of instructions or data structures and that canbe accessed, read, and/or executed by a computer, such as propagatedsignals or waves.

The program code may be executed by a processor, which may include oneor more processors, such as one or more DSPs, general purposemicroprocessors, ASICs, FPGAs, or other equivalent integrated ordiscrete logic circuitry. Such a processor may be configured to performany of the techniques described in this disclosure. A general purposeprocessor may be a microprocessor; but in the alternative, the processormay be any conventional processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of a DSP and a microprocessor, aplurality of microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration. Accordingly, the term“processor,” as used herein may refer to any of the foregoing structure,any combination of the foregoing structure, or any other structure orapparatus suitable for implementation of the techniques describedherein. In addition, in some aspects, the functionality described hereinmay be provided within dedicated software modules or hardware modulesconfigured for encoding and decoding, or incorporated in a combinedvideo encoder-decoder (CODEC). Also, the techniques could be fullyimplemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a codec hardware unit or provided by a collection ofinter-operative hardware units, including one or more processors asdescribed above, in conjunction with suitable software and/or firmware.

Various embodiments of the invention have been described. These andother embodiments are within the scope of the following claims.

What is claimed is:
 1. An apparatus for applying Rate DistortionOptimized Quantization (RDOQ), comprising: a memory device configured tostore a set of quantization schemes for use in encoding at least oneblock of video data, the set comprising an RDOQ quantization scheme anda non-RDOQ quantization scheme; and a processor in communication withthe memory device and configured to: determine at least one predictiontype for use in encoding the at least one block of video data based ondetermining the at least one prediction type having a lowest predictiontype complexity for the at least one block of video data; determine atleast one partition type for use in encoding the at least one block ofvideo data based on determining the at least one partition type having alowest partition type complexity for the at least one block of videodata; generate a first predicted video block for the at least one blockof video data; generate a second predicted video block different fromthe first predicted video block for the at least one block of videodata; apply the non-RDOQ quantization scheme to the at least one blockof the video data in determining the at least one prediction type and indetermining the at least one partition type based, on the firstpredicted video block and generate a best prediction type, in thenon-RDOQ quantization scheme, of the at least one prediction type and abest partition type of the at least one partition type during thedetermination of the at least one prediction type and the at least onepartition type; and apply the RDOQ quantization scheme, after the bestprediction type is generated in the non-RDOQ quantization scheme, to theat least one block for the determined at least one prediction type andthe determined at least one partition type based on the second predictedvideo block.
 2. The apparatus of claim 1, wherein the prediction typecomprises at least one of a merge mode, Advanced Motion VectorPrediction (AMVP) mode, or an intra-prediction mode.
 3. The apparatus ofclaim 1, wherein the partition type comprises at least one of a CodingUnit (CU), Transform Unit (TU), or Prediction Unit (PU).
 4. Theapparatus of claim 1, wherein the processor is further configured todetermine the at least one prediction type and the at least onepartition type via applying at least one prediction error criteria tothe at least one block of video data.
 5. The apparatus of claim 4,wherein the at least one prediction error criteria comprises at leastone of Rate Distortion (R-D), Sum of Absolute Difference (SAD), or Sumof Squared Differences (SSD).
 6. The apparatus of claim 1, wherein theprocessor is further configured to apply the RDOQ quantization scheme tothe at least one block for the at least one prediction type and the atleast one partition type.
 7. The apparatus of claim 1, wherein theprocessor is further configured to apply the RDOQ quantization scheme tothe at least one block for only the best prediction type and the bestpartition type.
 8. A method for applying Rate Distortion OptimizedQuantization (RDOQ), comprising: determining at least one predictiontype and at least one partition type for use in encoding at least oneblock of video data; generating a first predicted video block for the atleast one block of video data; generating a second predicted video blockdifferent from the first predicted video block for the at least oneblock of video data; applying a non-RDOQ quantization scheme to everycoefficient block of the at least one block of the video data indetermining of the at least one prediction type and in determining theat least one partition type based on the first predicted video block andgenerate a best prediction type of the at least one prediction type anda best partition type of the at least one partition type during thedetermination of the at least one prediction type and the at least onepartition type; and applying an RDOQ quantization scheme, after the bestprediction type is generated in the non-RDOQ quantization scheme, to theat least one block for the determined at least one prediction type andthe determined at least one partition type based on the second predictedvideo block.
 9. The method of claim 8, wherein the prediction typecomprises at least one of a merge mode, Advanced Motion VectorPrediction (AMVP) mode, or an intra-prediction mode.
 10. The method ofclaim 8, wherein the partition type comprises at least one of a CodingUnit (CU), Transform Unit (TU), or Prediction Unit (PU).
 11. The methodof claim 8, further comprising determining the at least one predictiontype and the at least one partition type via applying at least oneprediction error criteria to the at least one block of video data. 12.The method of claim 11, wherein the at least one prediction errorcriteria comprises at least one of Rate Distortion (R-D), Sum ofAbsolute Difference (SAD), or Sum of Squared Differences (SSD).
 13. Themethod of claim 8, further comprising applying the RDOQ quantizationscheme to the at least one block for the at least one prediction typeand the at least one partition type.
 14. The method of claim 8, furthercomprising applying the RDOQ quantization scheme to the at least oneblock for only the best prediction type and the best partition type. 15.A non-transitory computer readable storage medium having stored thereoninstructions that, when executed, cause a processor of a device to:determine at least one prediction type for use in encoding at least oneblock of video data based on determining the at least one predictiontype having a lowest prediction type complexity for the at least oneblock of video data; determine at least one partition type for use inencoding the at least one block of video data based on determining theat least one partition type having a lowest partition type complexityfor the at least one block of video data; generate a first predictedvideo block for the at least one block of video data; generate a secondpredicted video block different from the first predicted video block forthe at least one block of video data; apply a non-RDOQ quantizationscheme to the at least one block of the video data in determining of theat least one prediction type and in determining the at least onepartition type based on the first predicted video block and generate abest prediction type of the at least one prediction type and a bestpartition type of the at least one partition type during thedetermination of the at least one prediction type and the at least onepartition type; and apply an RDOQ quantization scheme, after the bestprediction type is generated in the non-RDOQ quantization scheme, to theat least one block for the determined at least one prediction type andthe determined at least one partition type based on the second predictedvideo block.
 16. The non-transitory computer readable storage medium ofclaim 15, wherein the prediction type comprises at least one of a mergemode, Advanced Motion Vector Prediction (AMVP) mode, or anintra-prediction mode.
 17. The non-transitory computer readable storagemedium of claim 15, wherein the partition type comprises at least one ofa Coding Unit (CU), Transform Unit (TU), or Prediction Unit (PU). 18.The non-transitory computer readable storage medium of claim 15, furtherhaving stored thereon instructions that, when executed, cause theprocessor to determine the at least one prediction type and the at leastone partition type via applying at least one prediction error criteriato the at least one block of video data.
 19. The non-transitory computerreadable storage medium of claim 18, wherein the at least one predictionerror criteria comprises at least one of Rate Distortion (R-D), Sum ofAbsolute Difference (SAD), or Sum of Squared Differences (SSD).
 20. Thenon-transitory computer readable storage medium of claim 15, furtherhaving stored thereon instructions that, when executed, cause theprocessor to apply the RDOQ quantization scheme to the at least oneblock for only the best prediction type and the best partition type. 21.A video coding device for applying Rate Distortion OptimizedQuantization (RDOQ), comprising: means for determining at least oneprediction type and at least one partition type for use in encoding atleast one block of video data; means for generating a first predictedvideo block for the at least one block of video data; means forgenerating a second predicted video block different from the firstpredicted video block for the at least one block of video data; meansfor applying a non-RDOQ quantization scheme to every coefficient blockof the at least one block of the video data in determining of the atleast one prediction type and in determining the at least one partitiontype based on the generated first predicted video block and generate abest prediction type of the at least one prediction type and a bestpartition type of the at least one partition type during thedetermination of the at least one prediction type and the at least onepartition type; and means for applying an RDOQ quantization scheme,after the best prediction type is generated in the non-RDOQ quantizationscheme, to the at least one block for the determined at least oneprediction type and the determined at least one partition type based onthe second predicted video block.
 22. The video coding device of claim21, wherein the prediction type comprises at least one of a merge mode,Advanced Motion Vector Prediction (AMVP) mode, or an intra-predictionmode.
 23. The video coding device of claim 21, wherein the partitiontype comprises at least one of a Coding Unit (CU), Transform Unit (TU),or Prediction Unit (PU).
 24. The video coding device of claim 21,further comprising means for determining the at least one predictiontype and the at least one partition type via applying at least oneprediction error criteria to the at least one block of video data. 25.The video coding device of claim 24, wherein the at least one predictionerror criteria comprises at least one of Rate Distortion (R-D), Sum ofAbsolute Difference (SAD), or Sum of Squared Differences (SSD).
 26. Thevideo coding device of claim 21, further comprising means for applyingthe RDOQ quantization scheme to the at least one block for only the bestprediction type and the best partition type.